AEROSEMI - Olimex

1 AEROSEMI . MT3608. High Efficiency 2A Step Up Converter FEATURES GENERAL DESCRIPTION. Integrated 80m Power MOSFET The MT3608 is a constant frequency, 6-pin SOT23. 2V to 24V Input Voltage current mode step-up converter intended for small, Fixed Switching Frequency low power applications. The MT3608 switches at Internal 4A Switch Current Limit and allows the use of tiny, low cost Adjustable Output Voltage capacitors and inductors 2mm or less in height. Internal Compensation Internal soft-start results in small inrush current and Up to 28V Output Voltage extends battery life. Automatic pulse Frequency modulation The MT3608 features automatic shifting to pulse Mode at Light Loads frequency modulation mode at light loads. The up to 97% Efficiency MT3608 includes under-voltage lockout, current Available in a 6-Pin SOT23-6 Package limiting, and thermal overload protection to prevent damage in the event of an output overload.

2 The MT3608 is available in a small 6-pin SOT-23. APPLICATIONS package. Battery-Powered Equipment Set-Top Boxed LCD Bais Supply DSL and Cable Modems and Routers Networking cards powered from PCI. or PCI express slots TYPICAL APPLICATION. Efficiency Efficiency (%). Iout (mA). Figure 1. Basic Application Circuit Figure 2. Efficiency Curve AEROSEMI Technology Co., Ltd 1. MT3608. ABSOLUTE MAXIMUM RATINGS. IN, EN voltages .. to 26V SW Voltage .. to 30V. Operating Temperature .. -40 C to +85 C Storage Temperature Range -65 C to 150 C. FB Voltages .. to 6V Peak SW Sink and Source Current 4A. Junction Temperature ..160 C Lead Temperature (Soldering, 10s) ..+300 C. PACKAGE/ORDER INFORMATION. SW 1 6 NC. GND 2 5 IN. FB 3 4 EN. SOT23-6. SOT23-5. (MT3608). (MT3540). PIN DESCRIPTION. PIN NAME FUNCTION. Power Switch Output. SW is the drain of the internal MOSFET switch. Connect the 1 SW. power inductor and output rectifier to SW.

3 SW can swing between GND and 28V. 2 GND Ground Pin 3 FB Feedback Input. The FB voltage is Connect a resistor divider to FB. Regulator On/Off Control Input. A high input at EN turns on the converter, and a 4 EN low input turns it off. When not used, connect EN to the input supply for automatic startup. Input Supply Pin. Must be locally bypassed. 5 IN. 6 NC NC. AEROSEMI Technology Co., Ltd 2. MT3608. ELECTRICAL CHARACTERISTICS. (VIN=VEN=5V, TA = 25 C, unless otherwise noted.). Parameter Conditions MIN TYP MAX unit Operating Input Voltage 2 24 V. Under Voltage Lockout V. Under Voltage Lockout Hysteresis 100 mV. Current (Shutdown) VEN= 0V 1 A. Quiescent Current (PFM) VFB= No switch 100 200 A. Quiescent Current (PWM) VFB= switch mA. Switching Frequency MHz Maximum Duty Cycle VFB = 0V 90 %. EN Input High Voltage V. EN Input Low Voltage V. FB Voltage V. FB Input Bias Current VFB = -50 -10 nA.

4 SW On Resistance (1) 80 150 m . SW Current Limit (1) VIN= 5V, Duty cycle=50% 4 A. SW Leakage VSW = 20V 1 A. Thermal Shutdown 155 . Note: 1) Guaranteed by design, not tested. AEROSEMI Technology Co., Ltd 3. MT3608. OPERATION. The MT3608 uses a fixed frequency, peak current The output voltage of the error amplifier the power mode boost regulator architecture to regulate MOSFET is turned off. The voltage at the output of voltage at the feedback pin. The operation of the the error amplifier is an amplified version of the MT3608 can be understood by referring to the block difference between the bandgap reference diagram of Figure 3. At the start of each oscillator voltage and the feedback voltage. In this way the cycle the MOSFET is turned on through the control peak current level keeps the output in regulation. If circuitry. To prevent sub-harmonic oscillations at the feedback voltage starts to drop, the output of the duty cycles greater than 50 percent, a stabilizing error amplifier increases.

5 These results in more ramp is added to the output of the current sense current to flow through the power MOSFET, thus amplifier and the result is fed into the negative input increasing the power delivered to the output. The of the PWM comparator. When this voltage equals MT3608 has internal soft start to limit the amount of input current at startup and to also limit the amount of overshoot on the output. Figure 3. Functional Block Diagram AEROSEMI Technology Co., Ltd 4. MT3608. TYPICAL OPERATING CHARACTERISTICS. Efficiency Curve Efficiency Curve Current limit(A). Efficiency Iout (mA) Iout(mA). line Regulation Load regualation Vout(V). Vout(V). Vin (V) Iout (mA). Freq VS Vin Efficiency VS Vin AEROSEMI Technology Co., Ltd 5. MT3608. APPLICATION INFORMATION. Setting the Output Voltage Layout Consideration The internal reference VREF is (Typical).The For best performance of the MT3608, the following output voltage is divided by a resistor divider,R1 and guidelines must be strictly followed.

6 R2 to the FB pin. The output voltage is given by Input and Output capacitors should be placed R1 close to the IC and connected to ground plane VOUT = VREF (1 + ) to reduce noise coupling. R2. The GND should be connected to a strong ground plane for heat sinking and noise Inductor Selection protection. The recommended values of inductor are to Keep the main current traces as possible as 22 H. Small size and better efficiency are the major short and wide. concerns for portable device, such as MT3608 used SW node of DC-DC converter is with high for mobile phone. The inductor should have low core frequency voltage swing. It should be kept at a loss at and low DCR for better efficiency. To small area. avoid inductor saturation current rating should be Place the feedback components as close as considered. possible to the IC and keep away from the noisy devices. Capacitor Selection Input and output ceramic capacitors of 22 F are recommended for MT3608 applications.

7 For better voltage filtering, ceramic capacitors with low ESR. are recommended. X5R and X7R types are suitable because of their wider voltage and temperature ranges. Diode Selection Schottky diode is a good choice for MT3608. because of its low forward voltage drop and fast reverses recovery. Using Schottky diode can get better efficiency. The high speed rectification is also a good characteristic of Schottky diode for high switching frequency. Current rating of the diode must meet the root mean square of the peak current and output average current multiplication as following : I D ( RMS ) I OUT I PEAK. The diode' s reverse breakdown voltage should be larger than the output voltage. AEROSEMI Technology Co., Ltd 6. MT3608. PACKAGE DESCRIPTION. TOP VIEW RECOMMENDED LAND PATTERN. FRONT VIEW SIDE VIEW. DETAIL A . Figure 4. TSOT23-6/SOT23-6 Physical Dimensions NOTE: 1)ALL DIMENSIONS ARE IN MILLIMETERS.

8 2) PACKAGE LENGTH DOES NOT INCLUDE MOLD FLASH,PROTRUSION OR GATE BURR. 3) PACKAGE WIDTH DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSION. 4) LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE MILLIMETERS MAX. 5) DRAWING CONFORMS TO JEDEC MO-193, VARIATION AB. 6) DRAWING IS NOT TO SCALE. 7) PIN 1 IS LOWER LEFT PIN WHEN READING TOP MARK FROM LEFT TO RIGHT, (SEE EXAMPLE TOP MARK). MT3608 Xi' an AEROSEMI Technology Co., Ltd T e l : 029-88868021 0755-82879616 021-51905952 7. Fax: 029-88445284 0755-82877171 021-51905952. E-mail: AEROSEMI Technology Co., Lt